This. I think I even have a cheaper version than that. Check Amazon for available washlets.
The mass-market Toto toilets are ~$250. Make sure you get the elongated bowl version. I have two in my house, one elongated and one round. The washlet for the round bowl was hard to source and it makes things somewhat cramped for larger people.
If I were doing it again, I'd replace the toilet with an elongated bowl version before adding a washlet.
